Elektroreduktion von 4,5-Dibrom-2,7-dinitrofluorescein an der tropfenden Quecksilberelektrode in wäßrigen Lösungen und in Wasser—Alkoholgemischen verschiedener pH-Werte

The polarographic reduction of 4,5-dibromo-2,7-dinitro-fluorescien (eosin bluish) at the dropping mercury electrode is investigated in buffered aqueous solutions as well as in water—methanol or—ethanol mixtures of different pH values. In aqueous solutions of low pH's 5–7 a small wave appears at the tail of the polarogram, which is attributed to the adsorption of the reduced form of eosin bluish. The results revealed that the furan ring is completely reduced at all pH's. The pyrone ring is partially reduced whereas the nitro groups are not involved in the electrode reaction. The kinetics of the electrode reaction are discussed.